Lava esthetic

The zirconia (Table 1) used in this study, Cercon xt ML (Dentsply Sirona, Charlotte, NC, USA) and Lava Esthetic (3M, St. Paul, MN, USA), were both precolored (A2 shade) 5Y-zirconia. Both zirconia samples had a multilayered structure, and a cutting machine was used (Accutom-100, Struers, Copenhagen, Denmark) to cut the specimens according to the layer fraction specified by the manufacturers (Figure 1). The upper and lower surfaces of the cut specimens were then sequentially dry polished with SiC-abrasive papers of 800, 1200, 2000, 3000, and 5000 grit sizes to reach a thickness of 1.25 mm for each layer (n = 5/layer), which was confirmed using micrometers (MDC-25PX, Mitutoyo, Kanagawa, Japan). Thereafter, sintering was carried out using a furnace (inLab Profire, Dentsply Sirona, Charlotte, NC, USA) following the manufacturer’s instructions for conventional and high-speed sintering (Table 2). Because the Lava Esthetic did not provide a high-speed sintering schedule, the schedule used for Cercon xt ML was applied for high-speed sintering of Lava Esthetic. The final dimensions of the sintered specimens were 10.0 × 10.0 × 1.016 mm³ (±0.008).